An OED is a device including at least one layer of an organic material capable of conducting a current. The OED includes an organic light emitting diode (OLED), an organic solar cell, an organic photo conductor (OPC), and an organic transistor.
Conventionally, an OLED, which is a representative OED, sequentially includes a substrate, a first electrode layer, an organic layer and a second electrode layer. In a structure known as so-called a bottom emitting device, the first electrode layer may be a transparent electrode layer, and the second electrode layer may be a reflective electrode layer. Also, in a structure known as so-called a top emitting device, the first electrode layer may be formed as a reflective electrode layer, and the second electrode layer may be formed as a transparent electrode layer. Electrons and holes injected by the electrode layers are recombined in the emitting layer located in the organic layer, resulting in generating light. The light may be emitted to the substrate in the bottom emitting device, or to the second electrode layer in the top emitting device. In the structure of the OLED, indium tin oxide (ITO) generally used as the transparent electrode layer, the organic layer, and the substrate, which is conventionally formed of glass, have refractive indexes of approximately 2.0, 1.8, and 1.5, respectively. In such a relationship of the refractive index, for example, the light generated in the emitting layer in the bottom emitting device is trapped at an interface between the organic layer and the first electrode layer or in the substrate due to a total internal reflection phenomenon, and only a very small amount of light is emitted.
An important factor considered in the OED is durability. Since the organic layer or electrode, and the like, is very easily oxidized under the influence of an external material such as moisture or oxygen, it is important to ensure the durability with respect to environmental factors. To this end, for example, the patent documents 1 to 4 suggest structures capable of preventing penetration of an external material.